Justification:
This species has an extremely small, severely fragmented range, and potentially as few as two viable subpopulations. Recent surveys suggest that the number of locations and mature individuals are both declining, and consequently it qualifies as Critically Endangered.

Camarhynchus heliobates is restricted to the Galápagos Islands, Ecuador. Historically, it was known from at least six mangrove patches on east Fernandina and east, south and west Isabela (Vargas 1997). Recent surveys have failed to record the species on Fernandina, and it seems likely that it is now extinct as a breeding bird on the island - the last reported sighting may have been in 1971 (Grant and Grant 1997). In 1997 and 1998, surveys on Isabela found breeding populations in only two areas, Playa Tortuga Negra and Caleta Black on the north-west coast of the island, with estimated populations of 37 and 21 pairs respectively (Grant and Grant 1997, Vargas 1997). Subsequent surveys have estimated the population at 36 and 16 pairs in 1999 (Vargas 1999), 24 and 14 pairs in 2007 (B. Fessl in litt. 2007), and perhaps the most thorough surveys to date recorded c.40 pairs in each in 2009 (Fessl et al. 2010). Surveys in the fairly extensive mangroves on the south-east coast of Isabela found three to five territories which probably contained breeding birds, but further areas of potentially suitable habitat remain unsurveyed (Dvorak et al. 1997, Dvorak et al. 2004). In 2008 several other historical sites were surveyed including Punta Espinoza (Fernandina), Bahia Elizabeth, Punta Moreno and Bahia Urbina, but the only site at which birds were located was Cartago Bay (Fessl et al. 2010, G. Young and B. Fessl in litt. 2008), from which the species is now thought extirpated, with no records from the area since 2009 (G. Young in litt. 2012).

It inhabits dense mangrove swamps, where it feeds on insects, larvae, spiders and some vegetable matter (Dvorak et al. 1997, Vargas 1997, Dvorak et al. 2004, Fessl et al. 2011). Its breeding season coincides with the beginning of heavy rainfalls, normally in December and January, and generally lasts until the end of the rainy season, around May, although successful nesting has been recorded as late as September (G. Young in litt. 2011). Nests are placed in tall trees within patches of high mangroves that are often flooded at high tide, a habitat that is rare on the Galápagos (Fessl et al. 2011). Mangroves used by the species in the north-west appear to be structurally different from areas where it is absent suggesting it has subtle habitat preferences and suffers from habitat degradation (Dvorak et al. 2004, Fessl et al. 2011). It appears to favour mangrove with tall trees, relatively low canopy cover and abundant leaf litter and dead wood (Dvorak et al. 2004, Fessl et al. 2011). A separation of the mangroves from the sea seems to be crucial as this prevents the washing out of leaf litter etc., which represents the species's preferred feeding substrates (Dvorak et al. 2004, Fessl et al. 2011).

This species is declining owing to predation and disease as a result of the presence of invasive species. Rattus rattus abundance is high at both breeding sites and is believed to be the major reason for the high nesting failure due to predation (70% in 2007) and low fledgling success (Fessl et al. 2010). Other possible introduced predators include feral cats (especially important during the post-fledging phase), Smooth-billed Ani Crotophaga ani and fire ants Solenopsis spp., although fire ants seemed to have been successfully exterminated in 1997 (Grant and Grant 1997, Vargas 1997, 1999). The blood-sucking nest parasite Philornis downsi represents a significant threat, as it is present in all nests and infestation is high (with a mean of 42 parasites per nest). The first case of nesting mortality due to Philornis parasitisation was recorded in 2007, and this threat is becoming relatively more prominent as invasive rodents are now controlled (G. Young in litt. 2012). Avian pox may also represent a significant threat to the species, which may also be inherently susceptible to the effects of inbreeding (Fessl et al. 2010). Research has shown that the species favours structurally distinct mangroves and hence may be susceptible to human modification of this habitat, and it may be especially susceptible to sea level rise driven by climate change (D. Wiedenfeld in litt. 2012).

Conservation Actions UnderwayThe habitat of this species is protected within the Galápagos National Park and, in 1979, the islands were declared a World Heritage Site, although this was classified as threatened in 2007. An action plan was published 2010 (in English and Spanish) following a workshop in 2008. Predator control is ongoing as is study into the control of Philornis downsi, with a workshop on this specific subject held in early 2012(G. Young and B. Fessl in litt. 2008, G. Young in litt. 2011, Fessl et al. 2010). A study of breeding biology commenced in 1999 (Vargas 1999) and a follow up study started in 2006. Blood samples are being analysed to investigate the genetic structure of the remaining population and to clarify whether hybridisation is occurring, although preliminary results for the latter are negative (H. Vargas and F. Cruz in litt. 2000). Preliminary results, however, do appear to indicate that the species is highly inbred (Fessl et al. 2010). A Darwin Initiative funded Mangrove Finch project coordinated by Galápagos National Park, Durrell Wildlife Conservation Trust and the Charles Darwin Foundation began in 2007 (G. Young in litt. 2007) with the aim of clarifying the need and proceedings for a breeding or translocation project. Possible sites for reintroduction have been visited on Isabela and habitat suitability assessments undertaken. Remote mapping of mangrove has taken place throughout Isabela with the aim of locating suitable sites, and captive trials have used Woodpecker Finch in order to train personnel and develop husbandry techniques that were then transferred to Mangrove Finch (G. Young and B. Fessl in litt. 2008). The first trial translocation took place in May 2010 when nine wild-trapped birds were taken to Bahia Urbina (25 km south of Playa Tortuga Negra) following intense rat control at this site (Cunninghame et al. 2011). Translocated birds proved hardy and, while able to find sufficient food and habitat at release site, may have returned to their source site (where one male was recorded after c.6 months). A conservation education programme has engaged local schoolchildren, and produced a film highlighting the species's importance. A course has been run for local guides (G. Young in litt. 2011).

Conservation Actions ProposedContinue to survey for further populations. Establish yearly monitoring at Playa Tortuga Negra and Caleta Black. Continue control measures for rats, wasps, ants, cats and fire ants at Playa Tortuga Negra and Caleta Black, and monitor effects on the population (Grant and Grant 1997). Further study the impact of Philornis downsi on adults and nestlings, and develop effective control methods, which may include application of control agents directly into nests (D. Wiedenfeld in litt. 2012). Study the impact of Galapagos Hawk Buteo galapagoensis. Facilitate printing of the species action plan in Spanish and English (G. Young in litt. 2011). Restore the Ramsar site at Vilamill. Establish translocation techniques to re-establish individuals at former sites following rat control, using head-started young birds less likely to return to their natal site (G. Young in litt. 2012).

Citation:

BirdLife International 2013. Camarhynchus heliobates. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 03 August 2015.